Timeline: move windowTimes management out of TimelineOverviewPane.

TOP did conversion from windowLeft and windowRight to windowTimes and vise versa with help
of Timeline(\w+)Overview objects which were TimelineView specific.
After that windowTimes were used by TimelineView part of the TimelinePanel.

I moved that conversion to the place where it is actually using.

BUG=
R=caseq@chromium.org

Review URL: https://codereview.chromium.org/119053004

git-svn-id: svn://svn.chromium.org/blink/trunk@164176 bbb929c8-8fbe-4397-9dbb-9b2b20218538